tunnel ram/ carburetor booster question

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UDUST81

UDUST81

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i recently purchased a weiand tunnel ram for my 505" wedge, i purchased two used holley 4779 750 double pumpers that i plan to rebuild and convert to e85 using the quickfuel metering blocks. i didnt realize until i got the two next to eachother that one has the "downleg" boosters and the other does not.

my main question is is this a big enough issue that i should pursue another carb with matching boosters or would it be a small enough difference to not make too big of an issue. im sure theyll be slightly off just not sure if its an extreme amount that will lead to tuning issues down the road...

any help is greatly appreciated thank you!
 
Generally the annual booster flows more fuel at a lower vacuum signal, and is definitely enough of a difference that I would look for 2 exact carbs.

I guess I should ask is the other one a annual booster?
 
This is a demon but the boosters are the same as Holley
Annual booster

019.JPG
 
not a pic of mine but they look like this, would this be considered a straight leg booster or annual as well?
SA330_FULLBOOK_Holley-Carbs-Rebuild_Page_025_Image_0003.jpg
 
To me that looks like a 650, What is the list #
 
4779-3 , throttle blades are 173 and 172 so pretty sure its a 750 double pumper... maybe an older design?
 
That's just a straight booster not a annual booster, normally you find these on a 650 because they are more restrictive than the open center down leg. You could call Holley in the morning but I bet they tell you not to run them together.
 
That's weird. I don't think I've ever seen a 4779 with a straight booster like that. Every one I've ever seen has down legs.

If it were me I'd do everything possible to make them the same. Exactly the same. I'd also make sure you have changeable idle and main air bleeds because you will need to work with them.
 
maybe they've been replaced some how although i thought they were a solid part of the main body on 4150's..... i may just look for a different main body for that one, would down leg boosters or annual boosters be better for a tunnel ram setup?
 
UDUST81 said:
maybe they've been replaced some how although i thought they were a solid part of the main body on 4150's..... i may just look for a different main body for that one, would down leg boosters or annual boosters be better for a tunnel ram setup?
Click to expand...
Can’t answer about the Annual boosters but on my car I ran two 650 DP Holleys, but I added two proform main body’s with down leg boosters. I used the base plates and the metering blocks from the 650DP carbs. They worked great on my 93 pump gas stock stroke 440. But if you don’t want to buy the proforms. I would try and find another 750DP with the down leg Boosters. I think they are soposed to flow Better
 
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